Problem: Solve for $y$ : $-13 = 3 + y$
Solution: Subtract $3$ from both sides: $ \begin{eqnarray} \\ \hphantom{-13 {- 3}} &\hphantom{=}& \hphantom{y} \\ -13 &=& 3 + y \\ \\ {-3} && {-3} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ -13 {- 3} &=& y \\ \end{eqnarray} $ Simplify. $ y = -16$